Digital broadcasting system

ABSTRACT

A digital broadcasting system is obtained having simple facilities and circuit structure and capable of efficiently transmitting and receiving synchronized pictures and displaying them without applying a synchronizing process thereto. 
     According to the digital broadcasting system, picture signals respectively for the light eye and the left eye obtained from two synchronously operated cameras ( 13   a   , 13   b ) are converted to a noninterlace frame signal (picture data) by a frame memory unit ( 20 ) of the transmitting end. The picture data is compressed and modulated, and then transmitted to a communication satellite ( 8 ) over a transmission line of one channel. A transmission signal supplied from the communication satellite ( 8 ) is demodulated and decoded, and then converted to picture signals for the right and left eyes by a frame memory unit ( 21 ) of the receiving end, and the converted signals are displayed on a stereoscopic display monitor ( 12 ) in a stereoscopic manner.

TECHNICAL FIELD

The present invention relates to a digital broadcasting system,particularly to a digital broadcasting system having a compressionprocessing circuit for transmitting and receiving a plurality ofpictures.

BACKGROUND ART

A conventional system used for providing a broadcasting serviceregarding video pictures transmits the pictures over a transmission lineof a single channel picture by picture, receives the transmittedpictures at a tuner picture by picture, and selects any picture to bedisplayed.

In other words, the conventional broadcasting system mentioned aboverequires a transmission line of a single channel for each picture inorder to simultaneously transmit a plurality of pictures.

In order to provide simultaneous transmission of two different pictures,for example, transmission lines of two channels are necessary, leadingto a problem that the transmission lines occupy twice the band requiredfor transmission of one picture.

On the other hand, the receiving end requires two tuners for receivingthese different pictures.

Further, if the pictures are synchronized with each other, the receivingend needs to carry out a process for synchronizing the pictures that areseparately received.

A resultant problem is that the broadcasting service to be implementedfor simultaneously providing two synchronized pictures has itsfacilities and circuit structure that are significantly complicate andlarge-scale, compared with the ordinary broadcasting service.

Accordingly, the present invention aims to provide a digitalbroadcasting system capable of efficiently transmitting and receivingpictures of two channels.

The invention further aims to provide a digital broadcasting systemwhich does not need a synchronizing process when synchronized picturesof two channels are transmitted and received.

The invention still further aims to provide a digital broadcastingsystem capable of achieving those aims with simple facilities andcircuit structure.

DISCLOSURE OF THE INVENTION

According to the invention, a digital broadcasting system includes apicture processing circuit generating picture data of one channel usinga first picture signal and a second picture signal, a transmissioncircuit compressing and modulating the picture data and thentransmitting the picture data, a reception circuit receiving thetransmitted picture data, and demodulating and expanding the picturedata, and a picture reproducing circuit receiving the demodulated andexpanded picture data to reproduce the first and second picture signals.

An advantage of the invention thus resides in efficient transmission andreception of two picture data over a transmission line of one channel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating an entire structure ofan ordinary digital broadcasting system.

FIG. 2 is a schematic block diagram illustrating a structure of thetransmitting end of a digital broadcasting system in the firstembodiment.

FIGS. 3A to 3C illustrate the processing of a frame memory unit of thetransmitting end in the first embodiment.

FIG. 4 is a schematic block diagram illustrating a structure of thereceiving end of the digital broadcasting system in the firstembodiment.

FIGS. 5A to 5C illustrate the processing of a frame memory unit of thereceiving end in the first embodiment.

FIG. 6 is a schematic block diagram illustrating a structure of thetransmitting end of a digital broadcasting system in the secondembodiment.

FIG. 7 is a schematic block diagram illustrating a structure of thereceiving end of the digital broadcasting system in the secondembodiment.

BEST MODES FOR CARRYING OUT THE INVENTION First Embodiment

The present invention enables pictures of two channels to be transmittedand received over a transmission line of one channel by generating anoninterlace frame signal of one channel (frame) from pictures of twochannels (fields) taken according to the current interlace system (NTSC)in the digital broadcasting system.

The embodiments presented below are described in relation to astereoscopic broadcasting service requiring pictures for the right andleft eyes respectively, that is implemented by employing as an exampleof the digital broadcasting system the one according to the 525progressive scanning system (hereinafter referred to as a noninterlacedigital broadcasting system) which is expected to be in increasingdemand in the future.

Details of such a noninterlace digital broadcasting system are found in,for example, “Development of CS Digital Broadcasting System Prototypefor 525-Progressive Scanning Signal” by Urano et al in Technical Reportof the Institute of Television Engineers of Japan, Vol. 20, No. 13, pp.25-30 published on Feb. 27, 1996.

FIG. 1 is a schematic block diagram illustrating for reference anexample of a basic structure of such a noninterlace digital broadcastingsystem. The illustrated system uses a communication satellite as anexample of the transmission system. The detailed specifications of eachcomponent described below are given by the above document andaccordingly, the details are not herein described.

Referring first to FIG. 1, the transmitting end in the noninterlacedigital broadcasting system includes a noninterlace system camera 1, apicture encoder 2, a sound collecting unit 4, a sound encoder 5 and amultiplexing unit 3.

Picture encoder 2 receives a picture signal obtained from a picturetaken by noninterlace system camera 1 and encodes (compresses) it.

In the compression process, the picture signal is converted to acollection of pixel data (hereinafter referred to as block) produced bydividing the picture signal into the pixel data consisting of BX data inthe horizontal direction and BY data in the vertical direction, andcorrelates them relative to each block and relative to blocks at thesame position in the preceding and following picture signals.

Such a compression process is represented by the international standardMPEG2 defined by the cooperative work group of MPEG (Moving PictureExpert Group) consisting of CCITT and ISO.

Sound encoder 5 encodes (compresses) a sound signal obtained by soundcollecting unit 4.

Multiplexing unit 3 applies transmission line coding to the compressedpicture signal and sound signal, multiplexes and outputs them.

A digital modulator 6 digitally modulates the multiplexed signalsupplied from multiplexing unit 3 to output it to a satellitecommunication equipment 7. Satellite communication equipment 7 transmitsthe signal to a communication satellite 8.

Referring again to FIG. 1, a system of the receiving end includes areceiving antenna for satellite broadcasting 9, a noninterlace systemadapted receiver 10, and a noninterlace system adapted monitor 11.

Receiving antenna for satellite broadcasting 9 receives a transmissionsignal from communication satellite 8.

Noninterlace system adapted receiver 10 demodulates the transmissionsignal received by satellite broadcast receiving antenna 9 and decodes(expands) it based on MPEG2.

Noninterlace system adapted monitor 11 displays an output fromnoninterlace system adapted receiver 10.

FIG. 2 is a schematic block diagram illustrating a basic structure ofthe transmitting end of a digital broadcasting system according to thefirst embodiment of the invention that can provide the stereoscopicbroadcasting service by employing the noninterlace digital broadcastingsystem described above. The components common to the structure of FIG. 2and the ordinary digital broadcasting system already shown in FIG. 1 arereferred to by the same reference numerals and characters, anddescription thereof is not repeated here.

A system structure of the transmitting end of the noninterlace digitalbroadcasting system in the first embodiment of the invention and itsoperation are first described.

Referring to FIG. 2, the transmitting end of the noninterlace digitalbroadcasting system in the first embodiment of the invention employsinterlace system cameras 13 a and 13 b as input devices for pictures.

The two interlace system cameras 13 a and 13 b are operated insynchronization with each other for taking a stereoscopic picture. Apicture signal R for the right eye is supplied from interlace systemcamera 13 a and a picture signal L for the left eye is supplied frominterlace system camera 13 b.

A frame memory unit 20 of the transmitting end receives at its input thepicture signal R for the right eye and the picture signal L for the lefteye obtained by interlace system cameras 13 a and 13 b respectively.

Frame memory unit 20 of the transmitting end writes the picture signal Rfor the right eye into one of two field memories (not shown) of thetransmitting end and writes the picture signal L for the left eye intothe other field memory. Frame memory unit 20 then reads field data (thewritten right eye picture signal R and left eye picture signal L) fromrespective field memories of the transmitting end at a rate twice thewriting frequency.

The signals are read in the order, for example, that the right eyepicture signal R (or the left eye picture signal L) corresponding to onefield is first read from one field memory of the transmitting end, andnext the left eye picture signal L (or the right eye picture signal R)corresponding to one field is read from the other field memory of thetransmitting end.

The number of effective pixels of an interlace field signal (picturesignal R for the light eye and picture signal L for the left eye),horizontal sync frequency FH, and vertical sync frequency FR are definedhere for a specific description below, for example, as 704 pixels in thehorizontal direction×240 pixels in the vertical direction, about 15.75kHz (15.75/1.001 kHz), and about 60 Hz (60/1.001 Hz) respectively.

Specifically, the writing frequency and the reading frequency aredefined as FH and (2×FH) respectively.

According to the format of picture data DATA obtained by the readingprocess, the number of effective pixels is 704 in the horizontaldirection×480 in the vertical direction, the horizontal sync frequencyis approximately 31.5 kHz (31.5/1.001 kHz), and the vertical syncfrequency is approximately 60 Hz (60/1.001 Hz). This format correspondsto the format of a standard noninterlace frame signal.

FIG. 3 illustrates the processing of frame memory unit 20 of thetransmitting end in the first embodiment of the invention, with FIG. 3Ashowing a structure of picture data DATA, FIG. 3B showing a structure ofpicture signal R for the right eye, and FIG. 3C showing a structure ofpicture signal L for the left eye.

In FIG. 3A, pixel data G (I, J) represents pixel data corresponding tothe horizontal number I (I=1-704) and the vertical number J (J=1-480)constituting picture data DATA.

The region of the matrix formed of pixel data G (I, J) corresponding toI=1-704 and J=1-240 (referred to simply as a first region) is formed ofpicture signal R for the right eye, and the region corresponding toI=1-704 and J=241-480 (refereed to as a second region) is formed ofpicture signal L for the left eye.

As clearly shown in FIGS. 3A to 3C, frame memory unit 20 of thetransmitting end converts interlace field signals of two fields (righteye picture signal R and left eye picture signal L) to a noninterlaceframe signal of one frame (picture data DATA).

Further, the interlace field signals constituting picture data DATA eachmaintain its original structure as a single signal, as clearly shown inFIGS. 3A to 3C.

When picture data DATA is compressed, picture signal R for the right eyeand picture signal L for the left eye are simultaneously compressed.Accordingly, picture data DATA supplied from field memory unit 20 of thetransmitting end is efficiently compressed in picture encoder 2.

It is noted that the same effect is achieved even if left eye picturesignal L is arranged in the first region and right eye picture signal Ris arranged in the second region.

Each circuit following picture encoder 2 operates as described inrelation to FIG. 1.

Consequently, a noninterlace frame signal (picture data DATA) of oneframe formed of picture signals of two fields is transmitted tocommunication satellite 8 over a transmission line of a single channel.

A system structure of the receiving end of the noninterlace digitalbroadcasting system in the first embodiment of the invention and itsoperation are next described.

FIG. 4 is a schematic block diagram illustrating a basic structure ofthe receiving end of the noninterlace digital broadcasting systemaccording to the first embodiment of the invention, in which thecomponents identical to those in FIG. 1 have the same reference numbersand characters, and description thereof is not repeated here.

Referring to FIG. 4, at the receiving end of the noninterlace digitalbroadcasting system in the first embodiment of the invention, picturedata DATA of one channel transmitted from communication satellite 8 isreceived by a receiving antenna for satellite broadcasting 9 anddemodulated and decoded by a noninterlace system adapted receiver 10, asalready described with reference to FIG. 1. According to the invention,noninterlace system adapted receiver 10 is internally provided with aninterface function for digitally outputting picture data DATA as it is.

A frame memory unit 21 of the receiving end receives picture data DATAdemodulated and decoded by noninterlace system adapted receiver 10, andwrites it into two field memories (not shown) of the receiving end.

Specifically, among pixel data constituting picture data DATA, pixeldata of the first region (e.g. picture signal R for the right eye ifpicture data DATA shown in FIGS. 3A to 3C is received) is written intoone field memory of the receiving end, and pixel data of the secondregion (e.g. picture signal L for the left eye) is written into theother.

Field data (the written right eye picture signal R and left eye picturesignal L) are respectively read from two field memories of the receivingend at the same timing and half the rate of the writing frequency.

Specifically, the writing frequency is (2×FH) and the reading frequencyis FH according to the example presented above.

FIGS. 5A to 5C illustrate the processing of frame memory unit 21 of thereceiving end in the first embodiment of the invention, with FIG. 5Ashowing a structure of picture data DATA, FIG. 5B showing a structure ofpicture signal R for the right eye, and FIG. 5C showing a structure ofRae picture signal L for the left eye.

FIGS. 5A to 5C clearly show that frame memory unit 21 of the receivingend converts picture data DATA transmitted over a single channeltransmission line to picture signal R for the right eye and picturesignal L for the left eye.

Specifically, frame memory unit 21 of the receiving end converts anoninterlace frame signal of one frame to an interlace field signalformat to reproduce picture signals of two fields (right eye picturesignal R and left eye picture signal L).

Picture signal R for the right eye and picture signal L for the left eyeare then converted to analog signals by a D/A converter (not shown) ifnecessary, and input to a stereoscopic display monitor 12.

Examples of stereoscopic display monitor 12 are of various types (e.g.the one using eyeglasses of the liquid crystal shutter system, “displayscreen reproduction system” without using eyeglasses, and the like).

So long as two interlace system cameras 13 a and 13 b operate insynchronization with each other, both of picture signal R for the righteye and picture signal L for the left eye supplied to stereoscopicdisplay monitor 12 are always picture signals obtained from picturesthat are simultaneously taken.

Therefore, when a stereoscopic picture is to be displayed onstereoscopic display monitor 12, a synchronizing process for light eyepicture signal R and left eye picture signal L is unnecessary.

The number of effective pixels used for the purpose of description inthe first embodiment of the invention is based on the standard value,and any other number of pixels is applicable. Any other values of thehorizontal sync frequency and the vertical sync frequency are alsoapplicable.

The compression efficiency would be enhanced if the number of effectivepixels is defined as any multiple of integer of the minimum block unitfor picture compression (e.g. 8 pixels×8 pixels when the MPEG standardis employed as a compression system).

Second Embodiment

According to the second embodiment of the invention, an effect achievedwhen the invention is applied to a broadcasting service (except for thestereoscopic broadcasting service) that provides two picturessynchronized with each other is described. It is noted that thenoninterlace digital broadcasting system shown in FIG. 1 is used as oneexample of the digital broadcasting system for the purpose ofdescription, similarly to the first embodiment.

FIG. 6 is a schematic block diagram illustrating a basic structure ofthe transmitting end of a noninterlace digital broadcasting system inthe second embodiment of the invention, in which the invention isapplied to the broadcasting service which provides two picturessynchronized with each other. Those components identical to those of thenoninterlace digital broadcasting system already shown in FIG. 1 havethe same reference numbers and characters, and description thereof isnot repeated here.

A system structure of the transmitting end of the noninterlace digitalbroadcasting system in the second embodiment of the invention and itsoperation are first described.

Referring to FIG. 6, the transmitting end of the noninterlace digitalbroadcasting system in the second embodiment of the invention employsinterlace system signal generating units 14 a and 14 b (e.g. VTR,camera, or the like) as an input device for pictures. Interlace systemsignal generating units 14 a and 14 b are synchronously operated tooutput picture signals. A picture signal A1 is output from interlacesystem signal generating unit 14 a and a picture signal A2 is outputfrom interlace system signal generating unit 14 b.

A frame memory unit 20 of the transmitting end receives at its inputpicture signals A1 and A2 obtained by interlace system signal generatingunits 14 a and 14 b respectively.

Frame memory unit 20 of the transmitting end writes picture signal A1into one of two field memories (not shown) of the transmitting end andwrites picture signal A2 into the other field memory, and reads them attwice the rate of the writing frequency, as described in the firstembodiment. The order of reading follows the same manner as thatdescribed in the first embodiment.

Specifically, frame memory unit 20 of the transmitting end convertsinterlace field signals of two fields (picture signal A1 and picturesignal A2) into a noninterlace frame signal of one frame (picture dataDATA).

The noninterlace frame signal of one frame is efficiently compressed bya picture encoder 2 as described in the first embodiment and thereafterprocessed by circuits of the subsequent stages to be transmitted to acommunication satellite 8 over a transmission line of a single channel.

A system structure of the receiving end of the noninterlace digitalbroadcasting system in the second embodiment of the invention and itsoperation are next described.

FIG. 7 is a schematic block diagram illustrating a basic structure ofthe receiving end of the noninterlace digital broadcasting system in thesecond embodiment of the invention, in which the components identical tothose of the digital broadcasting system already shown in FIG. 1 havethe same reference numerals and characters and the description thereofis not repeated.

Referring to FIG. 7, at the receiving end of the noninterlace digitalbroadcasting system in the second embodiment of the invention, picturedata DATA of one channel transmitted from communication satellite 8 isreceived by a receiving antenna for satellite broadcasting 9, anddemodulated and decoded by a noninterlace system adapted receiver 10 asalready described with reference to FIG. 4.

A frame memory unit 21 of the receiving end receives picture data DATAwhich is demodulated and decoded by noninterlace system adapted receiver10, and writes it into two field memories (not shown) of the receivingend as described already in the first embodiment. The frame memory unitthen reads field data (written picture signals A1 and A2) fromrespective two field memories of the receiving end respectively at thesame timing and half the rate of the writing frequency.

Frame memory unit 21 of the receiving end thus converts picture dataDATA transmitted on a transmission line of a single channel into picturesignals A1 and A2.

Specifically, frame memory unit 21 of the receiving end converts anoninterlace frame signal of one frame to an interlace field signalformat to reproduce picture signals of two fields (picture signals A1and A2).

A switching unit 22 receives these picture signals A1 and A2, andswitches them to output one of them.

Picture signal A1 or picture signal A2 selected by switching unit 22 issupplied to a display monitor 23.

The switching by switching unit 22 can be done arbitrarily by the user.

Accordingly, in the relay broadcasting of a baseball game, if a picturetaken from the backstop side (picture signal A) and a picture taken fromthe outfield side (picture signal B) are provided to the user using thenoninterlace digital broadcasting system of the invention, the user canappropriately select from different pictures that are simultaneouslypresented, via switching unit 22, any picture (picture signal A1 orpicture signal A2) which the user wants to watch.

Therefore, a program selected by the user can be displayed immediatelywithout switching of the channel. Various broadcasting services can thusbe provided at a higher speed.

According to the invention, picture signals of two channels obtainedfrom pictures taken according to the interlace system are converted topicture data of one channel to be compressed and transmitted, so thatthe picture signals of two channels can be transmitted and receivedefficiently over a transmission line of one channel as described above.

Further, the picture signals of two channels are transmitted andreceived as the picture data of one channel, so that a synchronizingprocess for the picture signals of two channels is unnecessary in themonitoring operation.

Both of the transmitting and receiving ends can be implemented withsimple facilities and circuit structure similar to those of theconventional digital broadcasting system.

What is claimed is:
 1. A digital broadcasting system, comprising:picture processing means for multiplexing a field picture signal for theright eye of an interlace system and a field picture signal for the lefteye of an interface system synchronized with each other in associationwith every corresponding even number field and every corresponding oddnumber field to generate a frame picture signal of one channel ofnon-interlace system, said picture processing means arranging a picturecorresponding said field picture signal for the right eye and a picturecorresponding said field picture signal for the left eye respectivelyinto regions formed by vertically dividing a picture corresponding saidframe picture signal of one channel; transmission means for compressing,modulating and transmitting said frame picture signal; reception meansfor receiving, demodulating and expanding said transmitted frame picturesignal; and picture signal reproducing means for receiving saiddemodulated and expanded frame picture signal and reproducing said fieldpicture signal for the right eye and said field picture signal for theleft eye.
 2. The digital broadcasting system according to claim 1,wherein said picture processing means includes field memories forrespectively storing said field picture signal for the right eye andsaid field picture signal for the left eye, and wherein said pictureprocessing means writes said field picture signal for the right eye andsaid field picture signal for the left eye into said field memoriessimultaneously for every corresponding even number field and for everycorresponding odd number field and reads said field picture signal forthe right eye and said field picture signal for the left eve from saidfield memories alternatively at the rate twice as fast as the rate inwriting to generate said picture signal of one channel.